This clever loop relies on the constant interplay between death and rebirth, fueled by the sacrifice outlet Goblin Sledder to send Putrid Goblin straight to the graveyard. Because of its persist ability, Putrid Goblin sneaks right back onto the battlefield, but it would normally be crippled by a -1/-1 counter; thankfully, Good-Fortune Unicorn steps in to instantly neutralize that drawback by bestowing a +1/+1 counter upon entry, as these two opposing counters annihilate each other through state-based actions. This leaves Putrid Goblin pristine and ready to be sacrificed all over again, letting you cycle through the process indefinitely to trigger any enter-the-battlefield, leave-the-battlefield, or death effects your heart desires.